Concentration measurements and detection of the presence of organic and non-organic materials is of great interest in a number of applications. In one example, detection of materials within human tissue is an increasingly important aspect of healthcare for individuals. The development of non-invasive measurement techniques for monitoring biological and metabolic agents within human tissue is an important aspect of diagnosis therapy of various human diseases and may play a key role in the proper management of diseases. The development of non-invasive measurement techniques for monitoring biological and metabolic agents within human tissue is an important aspect of diagnosis therapy of various human diseases and may play a key role in the proper management of diseases. One such material relevant to Alzheimer's is amyloid-beta.
Another example of a biological agent that may be monitored for within human tissue is glucose. Glucose (C6H12O6) is a monosaccharide sugar and is one of the most important carbohydrate nutrient sources. Glucose is fundamental to almost all biological processes and is required for the production of ATP adenosine triphosphate and other essential cellular components. The normal range of glucose concentration within human blood is 70-160 mg/dl depending on the time of the last meal, the extent of physical tolerance and other factors. Freely circulating glucose molecules stimulate the release of insulin from the pancreas. Insulin helps glucose molecules to penetrate the cell wall by binding two specific receptors within cell membranes which are normally impermeable to glucose.
One disease associated with issues related to glucose concentrations is diabetes. Diabetes is a disorder caused by the decreased production of insulin, or by a decreased ability to utilize insulin and transport the glucose across cell membranes. As a result, a high potentially dangerous concentration of glucose can accumulate within the blood (hyperglycemia) during the disease. Therefore, it is of great importance to maintain blood glucose concentration within a normal range in order to prevent possible severe physiological complications.
One significant role of physiological glucose monitoring is the diagnosis and management of several metabolic diseases, such as diabetes mellitus (or simply diabetes). There are a number of invasive and non-invasive techniques presently used for glucose monitoring. The problem with existing non-invasive glucose monitoring techniques is that a clinically acceptable process has not yet been determined. Standard techniques from the analysis of blood currently involve an individual puncturing a finger and subsequent analysis of collected blood samples from the finger. In recent decades, non-invasive blood glucose monitoring has become an increasingly important topic of investigation in the realm of biomedical engineering. In particular, the introduction of optical approaches has caused some advances within the field. Advances in optics have led to a focused interest in optical imaging technologies and the development of non-invasive imaging systems. The application of optical methods to monitoring in cancer diagnostics and treatment is also a growing field due to the simplicity and low risk of optical detection methods. In addition to the medical field, the detection of various types of materials in a variety of other environments would be readily apparent.
Many optical techniques for sensing different tissue metabolites and glucose in living tissue have been in development over the last 50 years. These methods have been based upon florescent, near infrared and mid-infrared spectroscopy, Raman spectroscopy, photoacoustics, optical coherence tomography and other techniques. However, none of these techniques that have been tried have proved completely satisfactory.
Another organic component lending itself to optical material concentration sensing involves is human skin. The defense mechanisms of human skin are based on the action of antioxidant substances such as carotenoids, vitamins and enzymes. Beta carotene and lycopene represent more than 70% of the carotenoids in the human organism. The topical or systematic application of beta carotene and lycopene is a general strategy for improving the defense system of the human body. The evaluation and optimization of this treatment requires the measurement of the b-carotene and lycopene concentrations in human tissue, especially in the human skin as the barrier to the environment.
Thus, an improved non-invasive technique enabling the detection of concentrations and presence of various materials within a human body or other types of samples would have a number of applications within the medical field.